Apparatus for making die castings



Oct. 2, 1962 F. A. JAGIELSKI 3,

APPARATUS FOR MAKING DIE CASTINGS Filed Aug. 12, 1959 2 Sheets-Sheet lIII 67 IN VEN TOR: TRANczs J4 arm SKI.

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Oct. 1962 F. A. JAGlELSKl 3,056,178

APPARATUS FOR MAKING DIE CASTINGS Filed Aug. 12, 1959 2 Sheets-Sheet 2INVENTOR: Hmzms JA 5151: SKI. w BY Jiml- ATTIC United States PatentOflhce 3,056,178 APiAl-RATUS F1112 M AKING DIE CASTINGS Francis A.Jagielski, 102 Leander Drive, Toledo 7, Ohio Filed Aug. 12, 1959, Ser.No. 833,340 16 Claims. (Cl. 22-70) This invention relates to a methodand apparatus for making sound die castings and more particularly itdeals with a device for exerting a relatively small pressure on thesurface of the incoming metal in a casting die and thus reducing oreliminating turbulence in the flow of metal during the injectionthereof.

It has long been a problem of the die casting industry to make castingsfree from defects such as voids, blisters, air bubbles and the like. Itis believed that most of these defects are caused by the metal cominginto the die so rapidly and so turbulently, that it freezes too quickly,resultin in the entraining of air and failure to fill blind holes andside chambers in the die cavity. These air bubbles, blisters, and thelike materially weaken a casting, but often they can only be detected byuse of X-rays.

In solving the problem, many schemes have been tried to completelyevacuate the die space before injection of the metal. However, theseattempts have been very costly and not always successful.

It is therefore an object of this invention to produce an eflicient,simple, effective, and economic device for attachment to a die castingmachine which will substantially eliminate the above mentioned castingdefects.

Another object of this invention is to produce a device which willsubstantially eliminate turbulence in the flow of metal into a die, andat the same time allow lower injection pressures to be used.

Another object of this invention is to produce a device which willeliminate any necessity for vents or for shimming the die halves and toeliminate all but one overflow pad, thus substantially reducing theamount of flash to be trimmed from the casting.

Another object of this invention is to provide an expansible chamberinto which the air trapped in a casting die may be displaced, whichentrapped air or gas acts as a buffer or deterrent to turbulence in themolten metal being injected into the die.

Another object of this invention is to insure that the same amount ofair is displaced from the die cavity and its connecting ducts each timea casting is made as well as to insure that the correct amount of metalis always injected for each casting.

Another object of this invention is to provide a method of die castingwhich will eliminate most casting defects.

In accordance with this invention a partable casting die is providedwith a gate and an inlet runner near the bottom of the cavity and asingle overflow pad near the top of the cavity. An expansible chambercomprising an air cylinder with a piston free to reciprocate therein maybe mounted on the machine. A conduit connects one end of said cylinderwith said overflow pad in the die. A relatively light spring may beadjustably mounted in the cylinder, resiliently forcing the pistontoward said one end of the cylinder. Therefore when the metal isinjected into the die cavity, the air in the cavity and its metalinjection duct is displaced into the cylinder, where it pushes back onthe piston and compresses the spring. The size of the chamber isadjusted so that it is expanded to its maximum size at the same timethat the die cavity is filled with metal, or in other words, the maximumvolume of the chamber is made substantially equal to the volume of thedie cavity and its injection duct. Therefore the only compression of theair or gas in the chamber which takes place is that required inovercoming the resistance of the chamber to expansion. The effect isthat of placing a very small back pressure on the incoming metal, sothat it flows in more slowly, eliminating splashing and turbulence, sothat the die is completely filled with no air bubbles trapped therein.In a die with many impressions, a plurality of expansible chambers maybe utilized, and the pressure on the spring may be adjusted tocompensate for different size the cavities, injection pressures and/ormaterials to be cast. In addition, a twin-compartment metal holding potmay be provided, with means to transfer molten metal from a storagecompartment to a charg ing compartment, so that the metal in thecharging compartment and in the injecting duct or nozzle will always beat the same level to insure that the volume of air or gas in the cavityand ducts connected to it corresponds to the volume set in theexpansible chamber.

The above mentioned and other features and objects of this invention andthe manner of attaining them will become more apparent and the inventionitself will be best understood by reference to the following escriptionof an embodiment of the invention taken in conjunction with theaccompanying drawings, wherein:

FIG. 1 is a vertical sectional view of a portion of a casting machineutilizing one embodiment of this invention;

iG. 2 is a view on an enlarged scale taken along line II-II of FIG. 1showing the die impressions and a pair of expansible chambers connectedthereto according to this invention;

FIG. 3 is a vertical sectional view similar to FIG. 1 showing animproved metal holding pot for this invention.

FIG. 4 is a plan view of only the pot in FIG. 3; and

FIG. 5 is a vertical sectional view taken along line VV of FIG. 4.

Referring now in more detail to FIGS. 1 and 3 of the drawings, a diecasting machine 16 is provided with a standard pot 11 lined withrefractory material for holding the molten metal to be cast, and thispot is provided with a gooseneck 12 having a nozzle 13 by means of whichthe metal is injected into the die. The pot or holding furnace 11 isalso provided with a charging cylinder 14, in this case mountedvertically. An aperture 15 in the cylinder 14 allows it to be filledwith molten metal from the pool 16. The charging piston 17 reciprocatesin the cylinder 14, and when it has passed the aperture 15, begins toinject the metal through the nozzle 13. Mounted above the chargingcylinder 14 is a shot cylinder 18 which is controlled by fluid pressurelines 19 and 20 and which controls the action of the piston rod 21 andcharging piston 17. The improved pot shown in FIGS. 3, 4 and 5 will bedescribed later.

The casting die, just as the shot mechanism in FIG. 1, is of standardconstruction. Mounted on the machine is a fixed platen 25 and a movableplaten 26 as shown by arrows 27, to which are connected the fixed coverdie half 28 and movable ejector die half 29, respectively. An ejectorrod 39 may be provided to withdraw the sprue 31' and eject the finishedcasting from the machine. The gate 3-1, the runners 32, 33, 34, and therisers 35, 36 carry the molten metal from the nozzle 13 to the dieimpressions A, B, C, D.

The die cavities shown in FIG. 2 are merely for the purpose ofillustration, as the cavity may be of any shape whatsoever to producethe desired casting. In this illustration, the runners 33, 34 feed thedie cavities B, D at their lower ends and risers 35, 36 lead to cavitiesA, C. Overflow pads 37, 38, are provided at the upper ends of theimpressions A, C, respectively.

Referring now to the expansible chamber, in FIG. 2 there are shown twounits, both of which may be identical and thus any part designated byreference numeral on one of the units is exactly the same on the otherunit. The expansible chamber 40 comprises a hollow cylinder FatentedOct. 2, 1962 41 having a bore therein and may be closed at one end withan integral bottom member 42. The cylinder 41 may be provided at itsupper end with flanges 43 to which may be attached a cover member 44 bymeans of screws 45 or other fastening elements.

Inside the cylinder bore, a piston 46 is free to reciprocate havingmounted thereon a standard O-ring or other sealing element 47. On theatmosphere side of the piston 46, a compression spring 49 or otherresilient element may bear, which may seat in a recess provided at leastin part by a skirt 50 on an adjustable stop 51. When the floating piston46 contacts the end of the skirt 50, the spring 49 preferably is notcompletely compressed.

The position of this adjustable stop 51 may be controlled by means of anexterior hand wheel 52 which may be mounted on a threaded stem 53engaging a tapped hole 54 in the cylinder cover 44, and which stem 53may engage the adjustable stop 51 by means of a collar 55 which willpermit relative rotational movement, but not relative axial movementbetween the stem and the stop. The adjustment of the stop 51 ispreferably made so that when the piston 46 contacts the edge of theskirt 50, the volume of the chamber in the cylinder 40 below the piston46 is substantially equal to the volume of the cavities in the die andthe associated ducts.

In order to permit the escape of air behind the piston 42, vents 57, 53which open to the atmosphere may be provided in the cylinder cover 44and the adjustable stop 51, respectively.

The space between the piston 46 and the cylinder bottom member 42communicates with the overflow pad 37 or 38 in the die block 28 by meansof a conduit 60 which may be rigid pipe or any flexible tubing, and apassageway 61 through the die block.

For convenience in illustration, the expansible chamber unit 46 has beenshown in FIG. 1 to be mounted on the stationary platen '25 by means of abracket 65 and bolts or other fastening elements 66. An elongated slotor window 67 may be provided through the upper or nonpressurized end ofthe cylinder wall 41, and graduations 68 may be marked upon the outercylinder wall to indicate the position of the stop 51 in the cylinder41. Also a pointer 69 may be attached to the adjustable stop 51 toindicate its position on the scale 68.

The operation of the expansible chamber unit attached to a die castingmachine will now be described: The machine having been opened to ejectthe previous casting, the die halves 28, 29 are brought together intointimate contact by means of the usual mechanism (not shown), and thusair is trapped in the space defined by the upper portion of gooseneck12, gate 31, runners 32, 33, 3 4, risers 35, 36, cavities A, B, C, D andconduit 60, 61. Then fluid pressure is admitted through the line 19 tothe shot cylinder 18, forcing down the charging piston '17, andinjecting the metal through nozzle 13, gate 31, and runners 32, 33, 34into the die cavities B, D, then up through risers 35, 36 into cavitiesA, C. As the molten metal fills up the die cavities the air displacedthereby has no place to escape except through the channels 61 leadingfrom the overflow pads 37, 38, and thus the floating pistons 46 areforced upward against the action of the springs 49. As the pistons 46are forced upwardly against the springs 49, the air in the cylinders 41and conduits 60, 61 and also in the unfilled portion of the die cavitiesis very slightly compressed. The result is that of placing a very smallback pressure on the surface of the metal coming into the die. Thussplashing and turbulence are eliminated, and the metal flows moresteadily and slowly and completely fills the die impressions, resultingin a sound casting free from defects such as blow holes, laminations,air bubbles, or the like. When the casting machine is being set up witha new die, the position of the adjustable stop 51 may be varied by meansof handwheel 52 as indicated by the pointer 69 on the scale 68 so thatthe piston 46 just contacts the stop 51 at the same time that the diecavities are completely filled. Thus the air is compressed no more thanenough to overcome the resistance of the spring 49, and any excess ofmetal injected up into the ducts 60 will be resisted by compression ofthe air in the cylinder 40.

In FIGS. 3, 4, and 5, an improved metal holding pot 111 is shown. Themetal injecting parts, such as the gooseneck 12, the nozzle 13, thecharging cylinder 14, and the shot cylinder 18 have already beendescribed. Attached to the piston rod 21 by means of an anchor plate orother means is a second piston rod 121. At the end of this second pistonrod is attached a second piston 122 which reciprocates in a secondcylinder 123, and thus the pistons 17 and 122 reciprocate together. Abracket having a forked end 124 extending around the piston rod 121 maybe provided at its upper end with an elongated slot 125 and a lockingnut 126 for adjustably attaching to the shot cylinder housing 18. Thefork 124 is adjusted to contact the plate 120 just after the normalstroke of the piston rod 121 is reached, and stop the motion of thepiston 17 in case of failure of the usual stroke-limiting means. Thiswould prevent the injection of too much metal into the die.

Attached to the second cylinder 123 and extending to the side walls ofthe pot is a dividing wall 127, which separates the pot into a chargingcompartment holding the metal pool 16, and a storage compartment holdingthe pool 128. When a shot is made and the piston 17 reaches its lowestposition, the top of the piston 122 is below an aperture 129 in thecylinder 123, so that the cylinder above the piston is filled with metalfrom the pool 128. A small hole 130 is provided at the bottom of thecylinder 123 to allow the metal therein to escape back into the pool 128as the piston 122 descends below the side of the aperture 129.

As the pistons 17 and 122 now raise, the metal in the cylinder 123 flowsout through a higher aperture 131 into the top of pool 16. Any excessmetal flows over the top of wall 127 back into the pool 128. Thus thelevel of molten metal around the charging cylinder 14 is kept up to thetop of wall 127, which is preferably at such a height that the metal inthe gooseneck 12 is just below the nozzle opening 13.

Through the side of the storage compartment may be placed an opening 132having its lowest point on the same level as the top of wall 127. Thus,should the pool 12% be overfilled, the excess will run off through thisopening 132, and the metal in the gooseneck will not rise above thenozzle opening 13. This is important, in order to prevent metal fromrunning into the die between shots, and from freezing there or in thenozzle, as Well as to prevent the volume of air in the injection ductfrom changing.

Any means of connecting the piston rods 21, 121 may be used, and theymay even have separate actuating cylinders timed to operate together.The Wall 127 could extend up to the top of the pot 111, and have a smalldepression therein to allow back-flow of the metal, or it may be madewithout any depression, and an opening could be formed in the side ofthe charging chamber to allow excess metal to drain off and away fromthe pot entirely in which case the opening 132 would also beunnecessary. The important feature is that the level of the metal in thegooseneck must stay constant, in order to displace the same volume ofair with every shot. This level cannot be above the nozzle opening, andthe lower it is, the more air will be displaced, so the level ispreferably just below the nozzle opening.

The following and other modifications may be made without departing fromthe scope of this invention: The unit maybe mounted on any type ofcasting machine, not necessarily the gooseneck type used herein forpurposes of illustration. The die cavities may be of any shapewhatsoever to conform to the design requirements of the part beingproduced, and there may be one, two or more cavities in each die,depending on their size. One expansible chamber unit may be provided foreach cavity, or each unit may serve a plurality of cavities, as shown inthe drawing. Instead of the spring 49 other means to resist the movementof the floating piston may be employed, such as for example, variablefluid pressure, or the piston may be replaced by a confined bellows, orthe like. If the adjustable stop 51 be used, any convenient means ofadjusting its position may be utilized such as a hand crank, or asliding stem with a locking collar; and the pointer and scale could bedispensed with and the position of the stem 53 could be utilized fordetermining the position of the adjustable stop. Also the unit may bemounted at any point on the casting machine, not necessarily on thefixed platen as shown herein for illustration.

While there is thus described above the principles of this invention inconnection with specific apparatus, it is to be clearly understood thatthis description is made only by way of example and not as a limitationto the scope of this invention.

What is claimed is:

1. A die casting machine comprising: a portable die having a fixedvolume cavity with a molten metal inlet duct at one end thereof and agas outlet duct at the other end thereof and said cavity being so formedbetween said ducts that molten metal may flow continuously from saidinlet duct to said outlet duct, means to entrap the gas in the cavitybefore injecting molten metal therein, means for injecting molten metalthrough said inlet duct into said cavity against said entrapped air,means directly connected to said outlet duct for receiving and confiningsaid entrapped gas from said cavity and exerting a gradually increasingpressure directly on the surface of said molten metal as it is injectedinto said cavity.

2. A machine according to claim 1 wherein said means for exerting apressure comprises a cylinder having a piston reciprocable therein andadapted to be moved by the air displaced in said die when said metal isintroduced.

3. A machine according to claim 1 wherein said inlet duct is at thelower portion of said die and said outlet duct is at the upper portionthereof.

4. A machine according to claim 1 wherein said means for injecting metalinto said cavity includes a pot, and a piston reciprocable in a cylinderin said pot, said inlet duct connecting said cylinder to said cavity,whereby each reciprocation of said piston injects molten metal from saidpot into said cavity.

5. A machine according to claim 2 wherein said piston is restrained frommovement by a resilient means.

6. A machine according to claim 4 wherein said pot comprises first andsecond compartments, said piston and cylinder being in said firstcompartment, and a second piston and second cylinder connected to saidsecond compartment, whereby the second piston transfers molten metalfrom said second compartment to said first compartment to maintain agiven molten metal level in said first compartment.

7. A machine according to claim 5 wherein said resilient means comprisesa spring backed up by an adjustable stop.

8. A machine according to claim 7 wherein the volume in said cylinderwhen said piston contacts said adjustable stop is substantially equal tothe volume of said cavity.

9. A die casting machine comprising a partable die, means for injectingmolten metal into said die under pressure through a first duct connectedto the lower portion of said die, means for closing the parts of saiddie to entrap air therein before the injection of said molten metal, anda second duct means connected at least to the upper portion of said dieand extending from said die for the escape of said air, and an air tightexpansible chamber for said air separate from said die and directlyconnected to said second duct means to place air pressure directly onthe surface of said incoming molten metal.

10. A machine according to claim 9 wherein said expansible chamberincludes resilient means for applying said pressure.

11. A machine according to claim 9 including means for adjusting the airspace in said expansible chamber to correspond to the volume of airdisplaced by said metal in said die.

12. A machine according to claim 9 including means for the tightlysealing of said die for maintaining a constant volume of said air insaid die and said first duct before the injection of said molten metal.

13. A machine according to claim 10 wherein said resilient meanscomprises a spring.

14. A die casting machine comprising: a die, first and second reservoirsfor holding molten metal to be injected into said die, an overflow wallbetween said reservoirs, a first cylinder in said first reservoir havinga discharge aperture along said wall into said second reservoir and anintake aperture below the normal level of said molten metal in saidfirst reservoir, a first piston reciprocable in said first cylinder frombelow said intake aperture to below said discharge aperture for pumpingsaid molten metal from said first reservoir into said second reservoirfor maintaining a given level of said molten metal in said secondreservoir defined by the top of said overflow wall, a second cylinder insaid second reservoir, and a second piston reciprocable in said secondcylinder for injecting said molten metal from said second reservoir intosaid die.

15. A machine according to claim 14 including means rigidly connectingsaid pistons for reciprocating both said pistons together.

16. A die casting machine comprising: a partable die, first and secondreservoirs for holding molten metal to be injected into said die, meansfor closing the parts of said die to entrap air therein before theinjection of said molten metal, a first cylinder in said firstreservoir, a first piston reciprocable in said first cylinder forpumping said molten metal from said first reservoir into said secondreservoir for maintaining a given level of said molten metal in saidsecond reservoir, a second cylinder in said second reservoir, a secondpiston reciprocable in said second cylinder for injecting said moltenmetal from said second reservoir into said die, duct means connected tothe upper portion of said die for the escape of said air entrappedtherein, and an expansible chamber for said air separate from the cavityof said die and connected to said duct means to place air pressuredirectly on the surface of said incoming molten metal.

References Cited in the file of this patent UNITED STATES PATENTS464,411 Rockman Dec. 1, 1891 1,595,783 Howes Aug. 10, 1926 1,697,741Vaughan Jan. 1, 1929 2,465,889 Lester et al Mar. 29, 1948 2,822,578Lobell Feb. 11, 1958 2,896,279 Nyselius July 28, 1959

